The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Planetary gear assemblies are remarkably versatile and adaptable devices. Various motor vehicle driveline components such as transmissions, differentials and transaxles make frequent and common use of planetary gear assemblies. Typically they are singly utilized to provide a speed reduction and torque increase or arranged in tandem and associated with clutches and brakes that interconnect or ground various elements of the planetary gear assemblies to provide multiple speed reductions and torque multiplications.
A simple planetary gear assembly comprises a centrally disposed sun gear, a planet gear carrier disposed generally about the sun gear and a ring gear disposed about the carrier. A plurality of planet gears rotatably mounted on shafts in the carrier engage both the sun and the ring gears.
There are, of course, many engineering issues regarding the design and manufacture of planetary gear assemblies. One involves the manner by which several planetary gear assemblies are arranged or packaged in a housing of a transmission that further includes clutches, brakes, interconnecting members and shafts. Ever increasing power and torque requirements, improved fuel economy, and improved longevity and robustness also apply more stringent specifications and smaller packaging space for designs.
Another engineering issue relates to lubrication. In certain configurations and in certain vehicle speed ranges, the rotational speed of the planet or pinion gears of a given planetary gear assembly may be quite significant, i.e., many thousand RPM. The rotational speed of the planet gear carrier may also be quite high. High planet or pinion gear speeds are not problematic per se but they do require sufficient lubrication not only to lubricate the pinion-bearing-pinion shaft interface but also to carry off heat generated by such high speed rotation at the interface.
The present invention is directed to providing an improved planetary gear set assembly which not only provides a more robust assembly but also provides improved lubrication oil paths to the planet bearings.